I have the K&N Typhoon 69 series (the chrome one) and I love it. It does feel like it provided a little extra in the seat, but where I really noticed a difference is the symphony under WOT. It seems to have made my exhaust louder under WOT, and to me, that is a good thing.
I will admit that I did not have a lot of seat time when I installed mine, so I probably wouldn't have be able to tell if there was a large difference.
K&N Typhoon CAI * Flowmaster American Thunder cat-back exhaust * Hurst Short Throw Shifter * Black Phantom Grille * Pioneer AVH-P8400BH - Scosche Dash Kit - Rockford Fosgate 3Sixty.3 - Rockford Fosgate T1000-1bdCP, T400-4, T1D215, T1692, T2652-S - SubThump 15" Camaro box - Dynamat Extreme - Stinger & Kicker RCA's - Monster, Tsunami, Streetwires, Scosche, and Kicker wiring - Stinger Distribution blocks - Tsunami Breakers - Tsunami and Rockford Fosgate set screw terminals